1. Definition

Lumbar puncture (LP) is a procedure in which a needle is inserted into the subarachnoid space of the lumbar spine to obtain cerebrospinal fluid (CSF) for diagnostic or therapeutic purposes.

Commonly done at L3–L4 or L4–L5 intervertebral space.

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2. Indications

A. Diagnostic Indications

1. Suspected CNS infection

• Meningitis
  • Bacterial
  • Viral
  • Tubercular
  • Fungal
• Encephalitis
• Brain abscess (supportive)
• Neurosyphilis

2. Neonatal sepsis evaluation

Important in:

• Neonates with positive blood culture
• Sepsis with neurologic signs
• Late onset sepsis
• Persistent unexplained illness

3. Neurologic disorders

• Guillain-Barré syndrome (albuminocytologic dissociation)
• Multiple sclerosis
• Demyelinating diseases
• Leukodystrophy

4. Malignancy

• Leukemia CNS involvement
• Lymphoma
• Medulloblastoma spread

5. Subarachnoid hemorrhage

When CT scan is negative but suspicion persists.

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B. Therapeutic Indications

• Intrathecal chemotherapy
• Intrathecal antibiotics
• Spinal anesthesia
• CSF pressure reduction (rare)

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3. Indications Specific to Neonates

Perform LP in neonates with:

1. Suspected meningitis
2. Positive blood culture
3. Seizures
4. Bulging fontanelle
5. Apnea / unexplained respiratory deterioration
6. Neurological abnormalities
7. Late onset sepsis (>72 hrs)

May delay LP in unstable neonate until stabilization.

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4. Contraindications

Absolute Contraindications

• Signs of raised intracranial pressure with mass lesion
• Cardiorespiratory instability
• Local infection at puncture site

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Relative Contraindications

• Severe thrombocytopenia (<50,000)
• Coagulopathy
• Spinal deformity
• Suspected spinal cord mass
• Severe shock

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5. Signs Suggesting Raised ICP (Do NOT perform LP immediately)

• Focal neurological deficits
• Papilledema
• Altered consciousness
• Unequal pupils
• Abnormal posturing
• Hypertension with bradycardia (Cushing triad)

These require neuroimaging first.

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6. Anatomy

LP is done below the conus medullaris.

Age	Conus level
Neonate	L3
Adult	L1–L2

Safe spaces:

• L3–L4
• L4–L5

Landmark:
Tuffier line (line joining iliac crests) → L4 vertebra

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7. Equipment

• Sterile gloves
• Antiseptic solution
• Sterile drapes
• Spinal needle with stylet
• Manometer
• 3–4 sterile tubes
• Local anesthetic (lidocaine)
• Syringes
• Adhesive dressing

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8. Needle Size

Age	Needle
Neonate	22–25G
Infant	22G
Child	20–22G

Typical length:

• Neonate: 1.5 inch
• Older children: 2.5 inch

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9. Position

1. Lateral decubitus (preferred)

• Knees flexed to chest
• Chin flexed
• Allows opening pressure measurement

2. Sitting position

Used when landmarks difficult.

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10. Procedure Steps

1. Position child
2. Identify L3–L4 or L4–L5
3. Clean with antiseptic
4. Sterile draping
5. Local anesthesia
6. Insert needle midline with stylet
7. Advance slowly
8. Feel “pop” entering subarachnoid space
9. Remove stylet → CSF flows
10. Collect CSF in tubes
11. Replace stylet and remove needle

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11. CSF Collection Tubes

Tube	Test
Tube 1	Biochemistry (protein, glucose)
Tube 2	Microbiology (Gram stain, culture)
Tube 3	Cell count
Tube 4	Special tests (PCR, viral studies)

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12. Opening Pressure

Measured with manometer.

Normal values:

Age	Pressure
Neonates	2–6 cm H₂O
Children	10–28 cm H₂O

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13. Normal CSF Values

Neonates

Parameter	Normal
Cells	0–20/mm³
Protein	40–120 mg/dL
Glucose	2/3 blood glucose

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Infants & Children

Parameter	Normal
Cells	0–5/mm³
Protein	15–45 mg/dL
Glucose	2/3 serum

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14. CSF Interpretation

Bacterial Meningitis

Finding	Result
Cells	↑ (100–10,000)
Cell type	Neutrophils
Protein	↑↑
Glucose	↓
Opening pressure	↑

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Viral Meningitis

Finding	Result
Cells	10–1000
Cell type	Lymphocytes
Protein	Mild ↑
Glucose	Normal

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TB Meningitis

Finding	Result
Cells	50–500
Type	Lymphocytes
Protein	↑↑
Glucose	↓

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15. Complications

Immediate

• Traumatic tap
• Pain
• Bleeding
• Infection

Post LP

• Post-LP headache
• Back pain

Serious

• Brain herniation
• Epidural hematoma
• Nerve injury

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16. Traumatic Tap Differentiation

Feature	Traumatic tap	SAH
RBC count	Decreases in later tubes	Same in all tubes
Clot	Present	Absent
Xanthochromia	Absent	Present

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17. Reasons for Failed LP

• Wrong level
• Poor positioning
• Obesity
• Dehydration
• Needle obstruction

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18. When NOT to Delay Antibiotics

In suspected meningitis:

• Start antibiotics immediately
• LP should not delay treatment

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19. Special Considerations in Neonates

• Higher CSF protein normally
• CSF WBC slightly higher
• LP often required in late onset sepsis
• May be delayed if unstable

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✅ Exam Pearls (Important for MD / Residency)

• Best site: L3–L4
• Neonatal normal CSF protein higher
• Always replace stylet before removing needle
• Opening pressure measured only in lateral position
• Papilledema → neuroimaging before LP

1. Definition

Creatine kinase (CK), also called creatine phosphokinase (CPK), is an intracellular enzyme that catalyzes the reversible conversion:Creatine+ATP↔Phosphocreatine+ADPCreatine + ATP \leftrightarrow Phosphocreatine + ADPCreatine+ATP↔Phosphocreatine+ADP

This reaction is crucial for energy storage and rapid regeneration of ATP, especially in muscle and brain tissues.

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2. Location in Body

CK is present mainly in tissues with high energy demand:

Tissue	CK concentration
Skeletal muscle	Highest
Cardiac muscle	High
Brain	Moderate
Smooth muscle	Low

Because CK is intracellular, serum CK rises when cell membrane damage occurs.

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3. CK Isoenzymes

CK exists in three isoenzymes, formed by combinations of M (muscle) and B (brain) subunits.

Isoenzyme	Structure	Major Source	Clinical significance
CK-MM	M + M	Skeletal muscle	Muscle injury, rhabdomyolysis
CK-MB	M + B	Cardiac muscle	Myocardial injury
CK-BB	B + B	Brain, smooth muscle	CNS injury

Distribution

• CK-MM: ~95–100% of total CK in normal serum
• CK-MB: <5% normally
• CK-BB: normally absent in serum

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4. Normal Values

Normal ranges vary by lab.

Typical reference:

Group	CK (U/L)
Adult male	50–200
Adult female	40–150
Children	Higher than adults
Neonates	Can be very high after birth

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5. Causes of Elevated CK

A. Skeletal Muscle Disorders

Most common cause.

Examples:

• Muscular dystrophy (e.g., Duchenne muscular dystrophy)
• Inflammatory myopathies
  • Polymyositis
  • Dermatomyositis
• Trauma
• Intramuscular injections
• Vigorous exercise

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B. Rhabdomyolysis

Massive CK elevation.

Causes:

• Crush injury
• Drugs (statins)
• Heat stroke
• Severe infections

CK may rise >5000–10,000 U/L.

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C. Cardiac Causes

CK-MB rises in myocardial injury.

Example:

• Myocardial Infarction

However, CK-MB is now largely replaced by troponins.

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D. Neurologic Disorders

CK-BB may increase in:

• Stroke
• Brain trauma
• Seizures

Example:

• Stroke

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E. Other Causes

• Hypothyroidism
• Alcohol abuse
• Surgery
• Prolonged immobilization
• Severe infections

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6. CK in Myocardial Infarction

Historically important marker.

Parameter	CK-MB
Rise	3–6 hours
Peak	12–24 hours
Normalization	48–72 hours

Used previously to detect reinfarction.

Now replaced mainly by troponin I/T.

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7. CK in Pediatric Practice

Important uses:

Screening for muscular dystrophy

Very high CK in:

• Duchenne muscular dystrophy
• Becker muscular dystrophy

Levels may be 10–100× normal.

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Evaluation of Hypotonia

Used when evaluating:

• floppy infant
• muscle weakness

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Evaluation of Rhabdomyolysis

Symptoms:

• myalgia
• weakness
• dark urine (myoglobinuria)

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8. Causes of Decreased CK

Rare clinical significance.

Seen in:

• Low muscle mass
• Chronic illness
• Pregnancy

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9. Drugs Causing Elevated CK

Important clinically.

Examples:

Drug	Mechanism
Statins	Myopathy
Antipsychotics	Neuroleptic malignant syndrome
Corticosteroids	Muscle breakdown

Example condition:
Neuroleptic Malignant Syndrome

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10. Investigation Panel When CK is Elevated

Test	Purpose
CK-MB	Cardiac source
Troponin	MI confirmation
AST / ALT	Muscle vs liver
LDH	Tissue injury
Serum myoglobin	Rhabdomyolysis
Urine myoglobin	Kidney injury

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11. CK in Rhabdomyolysis Severity

CK level	Interpretation
<1000	Mild
1000–5000	Moderate

5000 | Severe muscle injury |
15000 | High risk of renal failure |

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12. Clinical Pearls (Exam High-Yield)

• CK-MM → skeletal muscle injury
• CK-MB → cardiac muscle
• CK-BB → brain
• Duchenne muscular dystrophy → CK extremely high
• CK rises after muscle trauma/exercise
• CK-MB replaced by troponin in MI diagnosis

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✅ One-line exam memory tip

“CK rises with muscle damage — skeletal (MM), cardiac (MB), brain (BB).”